This invention relates to special brass with dezincification corrosion resistance, and more particularly, to special brass composed of copper and zinc as the main components, along with additions of antimony, lead and tin, plus a trace of impurities. This brass has excellent dexincification corrosion resistance and mechanical properties.
Generally, brass possesses excellent mechanical properties, resistance to dezincification corrosion and a beautiful gloss and is extensively used because it is inexpensive compared with the other copper alloys. However, it readily suffers from dezincification corrosion thereby causing a serious disadvantage. The problems which stand in the way of practical use of, for example, brassy parts for valves will be explained hereinafter.
The brassy parts for valves are chiefly composed of so-called 6-4 brass, namely, containing 60% of copper and 40% of zinc. Particularly, among the brassy parts for valves, a part to be used as a valve stem (which is manufactured from a free cutting brass bar or forging brass bar) is apt to be broken owing to dezincification corrosion thereby causing malfunction of the valve. The dezincification corrosion in brass tends to occur remarkably in sea water, polluted water and hot water. Especially, when copper pipe is used as a supplying pipeline in a high-rise building, through which hot water at temperatures of about 60.degree. C. to 80.degree. C. is supplied, there have been some cases in which the stem of a valve used in the pipelines suffers from dezincification corrosion within one to three years, thereby to prevent the valve from being used continuously.
In recent years, many copper alloy materials resistant to dezincification corrosion have been developed, but such corrosion resistance is not yet satisfactory. Although the addition of a poisonous substance has been considered for improving dezincification corrosion resistance of brass, it is unpractical. Thus, there is no alloy with dezincification corrosion resistance, which is satisfictory for practical use.